In my training plan, I do several "fast finish long runs" where I'll do the first 12 miles of a 20 miler at easy effort and then do the last 8 miles at MP or break it up by doing 2x4 miles at MP with a few minutes rest in between. That has really worked well for me. In training for my last marathon (Oct. 2012) I don't think I ran more than 8 miles at MP.

Very much agreed. Although you are getting a lot of tempo runs and speed work in the week, the Long run is also very essential in not only running it, but running it smart. It also depends on what stage of running you are at and what your goals are. But over all if you are wanting a time goal, it's important to get some MP in those long runs. Think of it this way - Although you are doing all of those work outs during the week, when you actually run at MP for an extended amount of time (Long Runs), this programs the body exactly what to do, so on race day, you know exactly what pace to run. You don't want to do this with every long run, but usually one out of three. There are a countless number of ways to break up a long run to do MP. Hal Higdon has good plans for a number a race distances, but the downfall is that they are not very specific, and lacks a variety of workouts that you will really benefit from. Remember this - Long Slow Distance = a Long Slow Distance Runner. Hope this helps some, and please note that this comes from my experience, and every one is different. All runners are not created equal, and so what works for one runner........well, you get the gist.

" Remember this - Long Slow Distance = a Long Slow Distance Runner."

Yup, this is my fear. I didn't do anything special for my HM training and I thought my time was terrible and that I could have pushed harder in training so I could grow as a runner not just do things to finish.

LSD = Long STEADY Distance, not slow.

I don't agree with this at all. Longer races (HM and up) are run at 97%+ aerobic. The way that you build the aerobic system is not by running 75 second quarters or 1/2 hill sprints. It's done by running a lot of miles over time. For a HM, a 40 mpw plan with intervals, tempo and hills is not going to produce as good a results as a 70 mpw plan with a tempo run and maybe some strides. I saw dramatic improvements in ALL race distance when my mileage consistently exceeded 40 mpw.

My marathon plan for last fall did not have an intervals, no Yassos, no hill work. I did a lot of easy, aerobic running with a tempo run of some sort once a week and some strides once per week. I was over 60 mpw for the 8 week heart of the training with some weeks exceeding 80 mpw. I did a fast finish long run probably every third long run. I would estimate that 85 of the miles that I ran were right around 9:00 per mile. What results did this produce?

I ran 3:12, that's a 7:21 average pace. I ran the last 4 miles in the 6:50s because of conservative pacing early. I didn't run a sub 7:21 mile until mile 18. This was a PR by 14 minutes from the previous fall.

How did this training impact my HM time? I ran a 1:28:05 6 weeks prior to the marathon during a 60 mile week. The previous week was over 80 miles. This was a 44 second PR from a race in March of the same year (which was a 2:00 PR from the previous year's HM best).

What I'm saying is, don't get hung up on thinking you need to run a lot of fast miles to get faster. It's been proven over decades that the way to improve is to build aerobic base by running lots of easy miles over time. There are no shortcuts.

I would add that Carson knows what he is talking about. Also, there is an element of "magic" that happens on race day that lets you run faster than you would expect. Of course, this magic depends on having done the training and run the volume necessary to make it happen.

My personal magic story happened in Jan 2012 after (restarting) running in Feb 2011. I ran a marathon at an 8:43 pace in Nov. after a week of recovery I simply ran as high a weekly volume (up to around 90 mi/week) as I could manage at what I thought at the time was an easy pace, generally 8:10 to 9:00/ mi. Sometimes a lot slower due to being too tired.

The first week of Jan, after a taper week, I ran a half marathon at a 7:17 pace for a 1:35:25 finish time. I had not run that pace in training before.

Easy pace volume works.

LSD = Long STEADY Distance, not slow.

This is what Runners World stated LSD - NOT the hallucinogen. LSD is an abbreviation for "Long, Slow
Distance," which refers to the practice of running longer distances
at an "easy" pace rather than shorter ones to exhaustion. The slower
pace allows the runner to go longer and, therefore (supposedly), gain
more fitness.
Steady would indeed make more sense how ever. I always thought it was long slow distance. Thanks for that clarification Carson. Now I know why I ended my RW subscription.

If you take a look at McMillan's Running calculator, you will see there there is very little difference between easy pace and long run pace. There is a misconception that you have to drastically slow down your easy run pace in order to go further. I contend that if you have to slow down considerably for your long run, then you are either running too far or you are running your easy runs too fast, probably way too fast. I think it most cases, it's the latter. If you are banging out 4 mile runs at 8:30 pace, yet you need to slow to 10:30 to get through 10, then you are most definitely running your easy runs way too fast.